Provided herein are single-substance multi-point calibration techniques for quantitative mass spectrometry using the theoretical relative abundance of isotopes in a calibrator. Also provided herein are methods of determining the concentration of an analyte using a calibrator for the analyte.

The invention discloses a method for the detection of sialate glycosyl casein glycomacropeptide by boronate affinity column enrichment-liquid chromatography-tandem mass spectrometry using phenylboric acid modified mesoporous silica as packing material, which belongs to the field of food analysis and detection. The method includes the following steps: (1) sample preparation; (2) enrichment and purification of boronate affinity column; (3) liquid chromatography-tandem mass spectrometry detection. The invention makes use of the affinity property of phenylboric acid to the special sugar group sialic acid on the serine and threonine residues in casein glycogiant peptide, regulates the adsorption and elution of casein glycogiant peptide with sialic acid group by changing pH. Combined with the high sensitivity and accuracy of liquid chromatography tandem mass spectrometry, it can be used for qualitative and quantitative analysis of casein glycomacropeptide with sialate glycol-group in phenylketonuria special medical formulations with complex matrix.

Methods and systems are provided herein for on-line preparation of a sample for mass spectrometry. In accordance with various aspects of applicant's teachings, the methods and systems can provide for the reduction of a polypeptide, for example, on a liquid chromatography column and can reduce or eliminate the need to incubate the reducing agent with the polypeptide and/or expose the reduced polypeptide to an alkylating agent.

When performing an analysis of the difference between a specific sample group and a nonspecific sample group, a principle component analysis processing unit (33) performs principle component analysis on a collection of a plurality of mass spectrums created from data obtained for a single specific sample, and a characteristic spectrum acquisition unit (34) acquires a characteristic spectrum for each of a plurality of principle components using factor loadings. A spectrum similarity calculation unit (35) calculates the similarities between all mass spectrums and the characteristic spectrum for each sample, and obtains a representative value for the same. The similarity representative value for each sample is obtained for all the characteristic spectrums. A difference determination unit (36) checks whether there is a significant difference between the distribution of the similarity representative values of the specific sample group and the distribution of the similarity representative values of the nonspecific sample group and determines that the characteristic spectrum which is the source of the similarities having a significant difference is a difference spectrum. The difference spectrum reflects component information characterizing a sample group difference, so a component identification unit (37) searches for the difference spectrum in a library to identify a component. This makes it possible to perform different analysis without performing spectrum peak detection.

Systems and methods are provided for analyzing a sample using overlapping measured mass selection window widths. A mass range of a sample is divided into two or more target mass selection window widths using a processor. The two or more target widths can have the same width or variable widths. A tandem mass spectrometer is instructed to perform two or more fragmentation scans across the mass range using the processor. Each fragmentation scan of the two or more fragmentation scans includes a measured mass selection window width. The two or more measured widths of the two or more fragmentation scans can have the same width or variable widths. At least two of the two or more measured mass selection window widths overlap. The overlap in measured mass selection window widths corresponds to at least one target mass selection window width.

The present application is directed to methods and systems for identifying small molecule compounds in mixtures using a library comprising calculated structures and corresponding calculated mass spectral fragmentation patterns of known and/or hypothetical small molecule compounds that may be in the mixture and screening of a mass spectrum of the mixture using the library to identify matching fragmentation patterns. If a mass spectral fragmentation pattern present in the mass spectrum of the mixture matches a calculated fragmentation pattern of one of the known or hypothetical compounds this confirms the identity of a compound in the mixture as the known or hypothetical compound. The method represents a platform method that can be used for a multitude of purposes related to the screening and identification of compounds in mixtures. Therefore the methods and systems of the present application represent an approach that is uniquely capable of navigating chemical space and providing a understanding of desired families and pharmacophores.

The present invention provides a compound of formula (I), formula (II), formula (III), (IV) or a salt thereof, compositions and methods of making the compound, methods and reagents for measuring the compound, and kits using the same. The use of a compound of formula (I), formula (II), formula (III), or formula (IV) for assessing or monitoring kidney function in a subject, determining predisposition to developing reduced kidney function, classifying a subject according to level of kidney function, and diagnosing or monitoring chronic kidney disease is also described.

Provided are methods of detecting the presence or amount of a vitamin D metabolite in a sample using mass spectrometry. The methods generally directed to ionizing a vitamin D metabolite in a sample and detecting the amount of the ion to determine the presence or amount of the vitamin D metabolite in the sample. Also provided are methods to detect the presence or amount of two or more vitamin D metabolites in a single assay.

The invention relates to methods for the detailed analysis of ion mixtures from complex mixtures of organic substances in time-of-flight mass spectrometers which are equipped with a trapped ion mobility spectrometer, a quadrupole mass selector and a fragmentation cell. The invention proposes to analyze ion signals of a first mass mobility map, fragment ion spectra and the identifications of the associated substances as to whether ion mixtures not resolved according to mass and mobility, for example from isomers or isobars, are possibly present, and to subsequently measure the ion signals of interest with method parameters which allow the ion species to be measured separately by means of high mobility resolution.

The invention discussed in this application relates to vitamin B12-based compounds that are useful as quantitative standards, particularly for the assessment of vitamin B12 deficiency.